LOA (m) LBP (m) B(m) D(m) T(m) V (Knots)

69.63 61 15.4 6.04 5.07 13

No of Screw 1 Type Spade Rudder

Step 1 RUDDER AREA

a

Ar 5.26 m2

b

A = TL/100 [1+25 (B/L) 2

] For normal seagoing ships

Where

A - Rudder area (m2)

T - Ships Draught (m)

A 8.02 m2 LBP - Ships Length (m)

c Average of Above two areas are taken as a Rudder Area

Ar 7 m2

Step 2 RUDDER GEOMETRY

Area = b * c T = 1.4b+X X = 0.05D-.0055D

X 0.26878

b 3.43 m b - Span

C - Chord

c 1.94 m

Aspect Ratio = Span / Chord AR 1.77

Step 3 RUDDER MAXIMUM ANGLE

a αmax = (5/7)*ԃmax Where,

αmax - Angle of Attack

ԃmax - Rudder deflection Angle

αmax 25 deg ԃmax = 33 - 35 for sea-going with conventional rudder

b Rudder Deflection Rate

ԃmin = (24 * V)/L

ԃmin 5.11 deg/sec

RUDDER CALCULATION

For normal supply vessels the range of rudder area is 3-4 % of (L*T)

Taking the rudder area to be 3.5 % of (L*T)

Using DNV Rule

Step 4 RUDDER PROFILE

Taper Ratio is taken as 0.5 Taper Ratio = Ct/Cr

C = (Ct + Cr)/2 Cr 2.58 m

Ct 1.29 m

Sweep back angle is taken to be 7 deg (Apporx)

Step 5 LOCATION OF RUDDER TURNING AXIS

a For Tip 0.122173

BC = b/2 tan 7 BC 0.2105413 m

BD = ct/4 BD 0.3226511 m

AC = EF = C/4 AC = EF 0.4839767 m

AD = AB+BD AD 0.5960865 m

b For Root

IJ = b/2 tan7 IJ 0.2105413 m

JL = Cr/4 JL 0.6453023 m

HI = EF = C/4 HI = EF 0.4839767 m

HL = HI+IJ+JL HL 1.3398203 m

KL = HL-HK KL 0.7437338 m

c Let's take 25% of Area to be at forward part of the rudder Stock

Ar/4 1.6597705 m2

Step 6 RUDDER CONSTRUCTION

a Rudder Stock ds = 83.3 Kr (FR(V+3)2(AR

2XPF

2+N

2)1/2

)1/3

Where,

Kr - Rudder coefficient 0.248

FR - Rudder profile coefficient 1

ds 158.885 mm Xpf = (0.12 * Ar)/6 0.133

Step 7 RUDDER BEARING

a Depth ZB = 1.25 ds Zb 198.61 mm

T= 0.2ds T 31.78 mm

b Clearance = 0.001*ds + 1 but not less than 1.5 mm

Clearance 1.2 mm

Step 8 RUDDER SCANTLING

a Plate Thickness

t= K(0.001Yw+0.61)[4-Yw /Xw](1.45+0.1(ds)1/2

)

Where,

K 1

Yw = Vertical spacing between the horizontal web in mm.

Xw = horizontal spacing of the vertical web in mm

ds = the basic stock diameter, mm

Yw 600 mm Xw 900 mm

t 10.93 mm

step 8 Rudder Construction

1 Rudder Stock

ԃs

where

Kr=Rudder coefficient = 0.248

FR= Rudder profile coefficient =1.0

V= Service speed =16 Kn

AR = Rudder area =10.5 m2

XPF = 0.12 AR / YR

YR =Depth of rudder at the center line of stock

step2

Rudder Bearing

Depth ZB = 1.2 ds Zb= mm

Minimum thickness of the wall for the lower bearing is to be taken as the lesser of

0.2ԃ or 100mm

T= 0.2ds T= mm

minimum7.0N/mm^2given bearing pressure on the projected area of the lowest

main bearing for metal

Basic stock diameter ds

ds = 83.3 Kr (FR(V+3)2(AR

2XPF

2+N

2)1/2

)1/3

LOA (m) LBP (m) B(m) D(m) T(m) V (Knots)

322.26 305.4 50.9 25.45 18.97 13

No of Screw 2 Type Spade Rudder

Step 1 RUDDER AREA

a

Ar 98.49 m2

b

A = TL/100 [1+25 (B/L) 2

] For normal seagoing ships

Where

A - Rudder area (m2)

T - Ships Draught (m)

A 98.17 m2 LBP - Ships Length (m)

c Average of Above two areas are taken as a Rudder Area

Ar 98 m2

Step 2 RUDDER GEOMETRY

Area = b * c T = 1.4b+X X = 0.05D-.0055D

X 1.132525

b 12.74 m b - Span

C - Chord

c 7.72 m

Aspect Ratio = Span / Chord AR 1.65

Step 3 RUDDER MAXIMUM ANGLE

a αmax = (5/7)*ԃmax Where,

αmax - Angle of Attack

ԃmax - Rudder deflection Angle

αmax 25 deg ԃmax = 33 - 35 for sea-going with conventional rudder

b Rudder Deflection Rate

RUDDER CALCULATION

For normal supply vessels the range of rudder area is 3-4 % of (L*T)

Taking the rudder area to be 3.5 % of (L*T)

Using DNV Rule

ԃmin = (24 * V)/L

ԃmin 1.02 deg/sec

Step 4 RUDDER PROFILE

Taper Ratio is taken as 0.5 Taper Ratio = Ct/Cr

C = (Ct + Cr)/2 Cr 10.29 m

Ct 5.14 m

Sweep back angle is taken to be 7 deg (Apporx)

Step 5 LOCATION OF RUDDER TURNING AXIS

a For Tip 0.122173

BC = b/2 tan 7 BC 0.7822023 m

BD = ct/4 BD 1.2862295 m

AC = EF = C/4 AC = EF 1.9293443 m

AD = AB+BD AD 2.4333715 m

b For Root

IJ = b/2 tan7 IJ 0.7822023 m

JL = Cr/4 JL 2.5724591 m

HI = EF = C/4 HI = EF 1.9293443 m

HL = HI+IJ+JL HL 5.2840057 m

KL = HL-HK KL 2.8506342 m

c Let's take 25% of Area to be at forward part of the rudder Stock

Ar/4 24.581879 m2

Step 6 RUDDER CONSTRUCTION

a Rudder Stock ds = 83.3 Kr (FR(V+3)2(AR

2XPF

2+N

2)1/2

)1/3

Where,

Kr - Rudder coefficient 0.248

FR - Rudder profile coefficient 1

ds 1414.525 mm Xpf = (0.12 * Ar)/6 0.360

Step 7 RUDDER BEARING

a Depth ZB = 1.25 ds Zb 1768.16 mm

T= 0.2ds T 282.90 mm

b Clearance = 0.001*ds + 1 but not less than 1.5 mm

Clearance 2.4 mm

Step 8 RUDDER SCANTLING

a Plate Thickness

t= K(0.001Yw+0.61)[4-Yw /Xw](1.45+0.1(ds)1/2

)

Where,

K 1

Yw = Vertical spacing between the horizontal web in mm.

Xw = horizontal spacing of the vertical web in mm

ds = the basic stock diameter, mm

Yw 600 mm Xw 900 mm

t 21.02 mm